The present application relates generally to an electrical wiring device and particularly to a ground fault circuit interrupter (GFCI) device.
GFCI devices are designed to trip in response to the detection of a ground fault condition at an AC load. Generally, the ground fault condition results when a person or object comes into simultaneous contact with a side of an AC load and an earth ground, a condition that can result in serious injury. The GFCI device detects this condition by using a sensing transformer to detect an imbalance between the currents flowing in the line and neutral conductors of the AC supply, as will occur when some of the current on the line side is being diverted to ground. When such an imbalance is detected, an electrically-held relay having primary power contacts within the GFCI device is immediately de-energized to place the primary power contacts in an open condition, thereby opening both sides of the AC line and removing all power from the load. Many types of GFCI devices are capable of being tripped not only by contact between the line side of the AC load and ground, but also by a connection between the neutral side of the AC load and ground. The latter type of connection, which may result from a defective load or from improper wiring, is potentially dangerous because it can prevent a conventional GFCI device from tripping at the intended threshold level of differing current between line and neutral when a line-to-ground fault occurs.